Photovoltaic modules are being used with increasing frequency to generate electricity. During daylight hours, the modules are exposed to sunlight that is converted to electricity, typically by an active semiconductor layer, or “active layer,” made of crystalline silicon.
In addition to generating electricity, the active layer generates a great amount of heat. This heat adversely affects the module. First, the heat reduces electric energy output of the module. In the typical case, energy output is reduced by approximately one half of a percent per degree Celsius in the temperature of the active layer. Second, the heat causes degradation of the module. In addition to ultimately causing failure of the module, the degradation further reduces the output of the module by approximately one percent per year during its life. These combined heat-related effects result in a significant reduction of energy output over the life of the module as well as a shortening of that life.
In view of the deleterious effects of heat on photovoltaic modules, various solutions have been proposed to remove heat from such modules. For example, bulk cooling in which conduction is used to remove heat from the module as a whole by way of the backplane of the module, has been proposed. Such solutions are not very effective, however, because the backplane is typically constructed of a polymer material that is a poor conductor of heat. Moreover, the encapsulant material typically used to seal the modules also limits the conduction of heat from the module.
Attempts have also been made to remove heat directly from the active layer. For example, holes have been provided through the backplanes of modules in hopes of removing heat from the active layers through convection. In other cases, thermally-conductive pins have been provided through the backplanes in hopes of removing heat from the active layers through conduction. Although such solutions may be effective in the short term, they are undesirable because they compromise the integrity of seals of the module, which can result in degradation from the ingress of moisture and oxygen. In addition, such solutions compromise the structural integrity of the module, which can lead to early failure. Furthermore, such solutions increase the cost and complexity of manufacturing the modules.
In view of the above discussion, it can be appreciated that it would be desirable to have an alternative means for removing heat from a photovoltaic module.